A rogue trader operating from a Memphis office made huge unauthorized trades in Chicago wheat futures on a day of epic volatility, costing the city's highest-volume commodities brokerage $141.5 million, the firm said Thursday.

MF Global, a futures firm incorporated in Bermuda with a major presence at the Chicago Board of Trade and Chicago Mercantile Exchange, said that it fired Evan B. Dooley, who had worked on commission in the firm's Memphis branch since November 2005. The firm, which has headquarters in New York, assured investors that the mechanism allowing Dooley to stake a hazardous bet in his personal account with company money had been corrected.

The acknowledgment represents an enormous blow to MF Global, whose financial position and stock price were rocked. The company also was put into the embarrassing position of admitting a catastrophic breach of the internal trading controls designed to protect the integrity of it far-flung operations. The $2.54 billion brokerage said it was not financially imperiled.

CME Group Inc., which owns the Board of Trade, confirmed that MF Global continues to meet capital requirements. But the cost of the rogue trades led to the firm's largest one-day loss ever and sent shock waves through the community of traders, who already were dumbstruck by Wednesday's extraordinary volatility in the wheat pits.

It was the erratic market for wheat on the Board of Trade that whipsawed Dooley, 40. While the full circumstances could not be determined Thursday, the firm said he built up a position of several thousand contracts in trading before dawn Wednesday as wheat plummeted. After learning of the position later Wednesday morning, MF Global liquidated it as prices fluctuated between $10.90 and $13.49 a bushel, a 25 percent price spread that rattled the nerves of even the most seasoned traders.

"We are deeply, deeply upset that this has happened," said MF Global Chief Executive Kevin Davis. "But we believe we fixed it and we believe it will never happen again. It's never happened to us, by the way, in the 32 years since the first electronic system arrived at this company."

Little was known Thursday about Dooley, who had worked in the Memphis branch since November 2005, when it was still part Man Group PLC.

Public records paint a more complex picture of Dooley than the one provided thus far by the brokerage, whose roots date to 1783. Dooley filed for bankruptcy in 2002. He owned the Dooley Trading Co. between 1995 and 2005. And two months after he joined MF Global, Dooley founded the Global Equity Exchange, according to Tennessee corporate filings.

The Global Equity Exchange bills itself as "the #1 Source of Private Equity Investors Worldwide!" and offers real estate investments, according to its Web site. Terry White, its chief executive, said Dooley is no longer involved with that company.

The $141.5 million loss constituted 6 percent of MF Global's capital and was more than four times the brokerage's most recent quarterly net income. MF Global shares fell more than 27 percent, to close Thursday at $21.19.

"'Rogue' is putting it mildly," said Tim Hannagan, senior grain analyst at Alaron Trading Corp. in Chicago. "This was dangerous."

In a conference call with analysts, Davis said MF Global had eliminated some trading controls because they slowed the execution process. It decided after Wednesday's loss to place controls on all systems, sacrificing some efficiency for security. Davis said it was possible insurance could cover some or all of the losses.MF Global hired an outside consultant to evaluate its procedures.

The company could not yet comment on whether Dooley's action might lead to criminal charges.

Wheat prices more than doubled in the past year after disappointing harvests worldwide, leading to domestic supplies hitting their lowest levels in 60 years.

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jboak@tribune.com

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About MF Global

MF Global is a broker of exchange-traded futures and options. It provides execution and clearing services across various trading markets.

Headquarters: New York

Where it operates: Offices in 12 countries and affiliations with more than 70 financial exchanges, including the Chicago Board of Trade and Chicago Mercantile Exchange.

Trading volume: Executes an average of 8.5 million contracts per day.

History: Separated from Man Group via an initial public offering in 2007. It is listed on the New York Stock Exchange (MF).